Evaluation Characterization And Management Of Naturally Occurring Radioactive Materials And Disused Radioactive Waste In Water And Soil Samples

In this study radiological hazards to members of the public and workers from exposurernto natural radioactivity as a result of mining activities from Kenticha Tantalum Minesrnin Ethiopia, have been studied through several exposure pathways using direct gammarnspectrometry to determine rn238rnU,rn 232rnTh, rn40rnK, rn226rnRa and rn222rnRn in tantalum ore, soil, waste,rnwaste tailing and water samples. Additionally, cancer risk assessment associated withrnNORM was estimated. The average activity concentrations ofrn238rnU,rn 232rnTh, rn40rnK, rn226rnRarnand rn222rnRn in tantalum ore were 78.653±1.431Bq/kg, 24.945±0.492 Bq/kg,rn603.170±55.013 Bq/kg, 69.478±31.0 Bq/kg and 112.554±50.249 kBq/mrn3rn,rnrespectively. In soil the activity concentrations were 69.354±1.081 Bq/kg,rn15.479±0.231 Bq/kg, 718.880±65.531Bq/kg, 68.923±1.7Bq/kg and 111.655±2.681rnkBq/mrn3rn, respectively and in solid waste samples 110.496±1.907 Bq/kg, 15.009±0.274rnBq/kg, 607.269±55.375 Bq/kg, 98.300±38.6 Bq/kg and 159.246±62.607 kBq/mrn3rnrnrespectively. The values were generally above the worldwide average activityrnconcentrations in all samples, except thorium-232.This might be due to the highrncontents of rn238rnU decay families and rn40rnK in the granite – pegmatite rocks of Kenticharnarea. The corresponding average external dose rate at 1m above the ground in air forrntantalum ore, soil and solid waste samples were 76.407 nGy/h, 71.337 nGy/h, 85.408rnnGy/h, respectively which were above worldwide average value of 60 nGy/h. Thernannual equivalent doses were also estimated as 0.021±0.003 mSv, 0.020±0.001 mSvrnand 0.023±0.004 mSv for ore, soil and solid waste samples, respectively and werernfound to be lower than the worldwide average of 2.42 mSv/y. Likewise, the radonrnemanation coefficient which is the fraction of radon generated within the grains ofrnmaterials and escaped to the pore space, varied from 82±2% to 85±2% for ores, fromrn82±2% to 84±2% for soil, and from 53±15% to 83±15% for solid waste samples. Also,rnthe radon exhalation rate varied in the range of 41.7±25.7 to 87.3±25.7 mBq/mrn2rn.s forrnores, from 56.2±1.4 to 58.1±1.4 mBq/mrn2rns for soil and from 53.3±32.1 to 120.2±32.1rnmBq/mrn2rns for solid waste, respectively. The radium equivalent activity, external hazardrnindex, internal hazard index and representative gamma index, for all samples werernestimated and generally found to be within recommended international values. Annualrneffective dose was evaluated from only external gamma dose rate. However, thernrelatively high values in all the other parameters measured implies that the Kenticharntantalum mine and its environments shown the significance of naturally occurring radioactive material. Therefore, the results from this study will ignite in decisionmakingrnforrnfuturernset-uprnofrnfurtherrnresearchrnforrnthernmanagementrnofrnNORMrnwastesrninrnrnKenticharntantalumrnminernandrnforrnthernemergingrnminingrnindustryrninrnEthiopia.rnRadioactivernrnmaterialrncontainingrnCs-137,rnRa-226,rnCo-60,rnSr-90rnandrnAm-241rnwererntreatedrnusingrnthernrndevelopedrnmethod.rnInrnthernmethodrndifferentrntypernofrnmaterialsrn(cement,rnsands,rnconcrete,rnrnetc.)rnrnwere tested for absorption of radiation emitted from the source as well asrnsuitability of the material for storage for long time. It was found that the best materialsrnto be used in radioactive waste treatment is Concrete, where the surface dose reducedrnfrom 150 to 3 µsave/h. In addition, design of storage container was proposed (withrnspecification). Finally, based on indications of the present research findings andrnscientific background, recommendations were forwarded to help on amending nuclearrnwaste management problems or indicate for other possible alternatives such asrnradiation map of Ethiopia.

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